Higher tier
What are free electrons?
The All elements are made of atoms. An atom consists of a nucleus containing protons and neutrons, surrounded by electrons. in a metal are held together by strong bonds.
The atoms are close together and in a regular arrangement.
Metal atoms have loose electrons in the outer shells that can move from atom to atom.
These loose electrons are called free electrons.
They can move freely throughout the metal.
An electric current in a metal is the flow of these free electrons in one direction.
Direction of flow of free electrons
Energy is required to make the free electrons travel in one direction.
An electric cell, or a battery, can supply this energy and make free electrons move in a metal conductor connected between its two terminals.
Electrons flow from the negative terminal of the battery, through the conductor to the positive terminal.
They are repelled by the negative terminal and attracted by the positive terminal.
The direction of conventional current
Electric current was discovered before physicists knew about free electrons.
It was originally thought that the current was flowing in the opposite direction, i.e. from the positive terminal of the battery, through the conductor, to the negative terminal.
For a number of reasons, although this is now known to be the wrong direction, it is still the direction of current marked on all circuit diagrams.
It is called the direction of conventional current.
Key points - Higher tier
- An electric current in a metal is a flow of free electrons in one direction.
- The direction of conventional current is from the positive terminal of a battery, through the conductor, to the negative terminal.
- The direction of free electron flow is from the negative terminal, through the conductor, to the positive terminal.
- The direction of conventional current is the direction marked on all circuit diagrams.
- The symbol for electric current is I.